Internal combustion engines, including, e.g., automobiles engines commonly include a head connected to the engine block and through which intake air is mixed with gas and ignited in cylinders in the block to drive pistons in the cylinders to turn a crank shaft. The products of combustion are also exhausted through the head after ignition and directed from the head into an exhaust manifold before flowing through the exhaust train of the vehicle and out, e.g., the tail pipe. Modern automobile engines commonly include multiple intake and exhaust ports opened and closed via multiple valves driven by one or more camshafts. Such engines are sometimes referred to as dual overhead cams (DOHC) or quattrovalve engines. On the exhaust side of the engine cycle, the manner in which the combustion products from each of multiple ports from a cylinder meet and mix with one another before being exhausted from the engine can affect the power and efficiency of the engine. As such, optimizing flow conditions and reducing back pressure of the combustion products exhausted from an internal combustion engine are important design criteria for modern automobile engines.